Testing the Fixed-hotspot-moving-plate model
University of British Columbia
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Students examine hot spot tracks, magnetic inclination data, and coral data from the Hawaii-Emperor Seamount Chain to test the hypothesis that hotspots are fixed. Most students have learned somewhere that hotspots are fixed, period. These data give them an opportunity to challenge that hypothesis.
This activity is appropriate for any introductory level Earth Science course. I use it in my Earth and the Solar System
Skills and concepts that students must have mastered
Students must be able to explain the sources of remnant magnetism and the relationship between magnetic inclination and latitude. Students must be familiar with the interior structure of the Earth and with the concept that lithospheric plates move horizontally on Earth's surface. Students must be able to explain the simplest model for the formation of hot spot tracks. Students need to be able to use x-y plots.
How the activity is situated in the course
Content/concepts goals for this activity
Reconstruct a portion of Earth's plate tectonic history based on magnetic inclination (and other) data.
Higher order thinking skills goals for this activity
Using data to examine a common simplification of how Earth works. Decide among hypotheses based on data rather than on what one has (perhaps) learned in the past.
Other skills goals for this activity
Students work in groups and discuss the activity and data, but each completes the activity individually.
Description of the activity/assignment
Students have read about Earth's magnetism, magnetic inclination, and how remnant magnetism can be used to reconstruct plate motions and they have completed a quiz on these topics. This activity presents them with data from Tarduno et al., 2003, published in Science (vol 301, p 1064-1069) and asks them to examine the fixed-hotspot model in light of these data. The activity asks them to interpret magnetic inclination data (and coral data) and reconstruct a plate motion/hotspot motion scenario that agrees with the evidence.
Determining whether students have met the goals
On an exam after this activity, I pose a very similar question, but for an imaginary scenario that does not exist on Earth (to my knowledge). Students who can synthesize orientations of hot spot tracks (volcano locations), volcano ages, and magnetic inclination data into a scenario that explains the data can answer this question correctly with a few words and/or a few arrows. Students who have previously learned that hotspots are fixed and have not been able to consider other options tend to ignore the data given in the exam question. Anecdotally, there's usually at least one student who approaches me after class, either excited by the added complexity of hotspots, or frustrated because the activity goes against a strong idea they hold.
More information about assessment tools and techniques.
Teaching materials and tips
Tarduno et al., 2003. "The Emperor Seamounts: Southward Motion of the Hawaiian Hotspot Plume in Earth's Mantle", Science, vol 301, p 1064-1069.